In the manufacture of cartons, a paperboard blank is fed between pairs of coacting upper and lower slotting heads which selectively cut slots in the blank. Each of the upper slotting heads is provided with one or more male slotter knives and each of the lower heads is provided with a pair of axially spaced, annular cutting discs. The annular cutting discs form a peripheral groove for receiving the cutting edges of the male slotter knife.
The length of the male slotter knife determines the length of the slot. Long slotter knives are very expensive and it is necessary for carton manufacturers to stock a large assortment of knife sizes.
The cutting edges of the male slotter knife eventually become chipped as the male slotter knife enters the peripheral groove in the lower slotting head. Also, metal-to-metal contact between the male slotter knife and the groove wears down the cutting edges on the male slotter knives, requiring that they be replaced more frequently than is desirable in order that the slot be cut cleanly. Replacement of the male slotter knives is a major repair and requires realignment of the upper and lower slotting heads.
To alleviate the above problems, the present invention provides a slotter knife with a holder capable of mounting one or more replaceable cutting elements for building up a longer knife of a needed size. The replaceable cutting elements provide for quick and easy sharpening of the slotter knife without requiring detachment of the holder from the slotting head and major realignment.
In a slitting head, the slitting knives are butted end-to-end for trimming the side edges of the blank. The knives for the slitting heads are generally similar to the knives for the slotting heads and so are the problems.